Black Library Submissions Window
Every Spring, Black Library holds an open window for writing submissions. Fa/tg/uys will rant at length at how they are sure to get in, and how they'll fix everything when they do.
You will never work for the Black Library
The Black Library is a small publishing house with its growth actively restricted by GWHQ. This means it has a tiny number of staff, most of whom are paid below the industry standard. They are selected for pliability and dedication rather than skill.
It is an open secret that ex-Games Workshop staff in good standing get more than one shot at being commissioned as freelance Black Library writers. (This is partially because GW does pay reasonable royalties to writers). They are plenty of ex-GW design staff who now write for Black Library (Gav Thorpe and Graham McNeill being the most notable), and that is not a coincidence. Active freelancers who aren't ex-GW are either friends of the staff, prominent GW bloggers or married to GW staff. They are also a handful of experienced tie-in writers who work freelance for BL, and they push most of the sales, but these are much less common than the bulk of the staff, who get the gig through nepotism.
In 2012 1800 people sent documents to Black Library during their open submissions window. Of these, 12 were chosen. 2 were experienced and published authors, 8 were ex-GW Employees (or friends of current employees) and 2 were totally new. Of these 12, only 1 got a novel deal. This is well below average for the publishing industry.
They currently have an 'open window' when it comes to submissions, which started in early 2015. It has yielded no results, and recruitment continues to be done via nepotism and cronyism.
In 2008, a former commissioning editor for Black Library admitted that the open window was mostly a publicity stunt designed to drive sales. This technique is a low-budget form of marketing, and was pioneered by the BBC in the 80's to encourage sales of Doctor Who novels. If you're not convinced, check out the sections of each submission window announcement where they list off "books to help you get into the groove of writing for 40k". Most of the books listed in each respective announcement are released around the time the announcement was posted. It's almost as if the whole thing is a scheme to drive grognards into buying their new novels in the hopes of becoming the next big writer. Hmm...
By 2018, things had improved a little. Black Library actively sought out staff from the rest of the industry, and the submissions process did conclude in a timely fashion. It has gotten better, but their reputation is still terrible. Their 2019/2020 submissions window ended abruptly with mass rejections.
You want to be published through the Black Library? Try getting published anywhere else first, it's easier.